Adaptive Howling Suppression Using Frequency Subband Attenuation
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Solution Overview
Problem
During Voice over Internet Protocol (VoIP) communication sessions, acoustic coupling between devices can cause feedback loops, leading to uncontrollably loud audio and a negative user experience, as devices in proximity recapture audio output, resulting in howling that must be manually muted.
Innovation Solution
A system and method for adaptive feedback reduction, where a device monitors input audio data, determines the presence of feedback in individual frequency subbands by comparing actual and expected values, and attenuates affected subbands to suppress howling, thereby improving user experience without manual intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If devices are placed in proximity for communication, then communication quality improves, but acoustic coupling causes feedback loops and howling
Solution Approach 1:
The patent segments the audio signal into multiple frequency subbands and processes each subband independently to detect and suppress feedback. By dividing the audio spectrum into discrete frequency ranges, the system can identify and attenuate specific feedback frequencies without affecting other audio components, thereby resolving the feedback loop issue while maintaining communication quality.
Solution Approach 2:
The patent implements a feedback detection mechanism that continuously monitors audio signals for feedback conditions. By comparing actual audio levels against expected levels in each frequency subband, the system detects feedback loops in real-time and applies automatic gain reduction to suppress the feedback, thus eliminating the harmful effect while preserving the communication function.
2Object-affected harmful factors
If manual muting is used to stop howling, then feedback suppression works, but user convenience deteriorates
Solution Approach 1:
The patent implements an automatic feedback suppression system that detects and mitigates howling without requiring user intervention. The system continuously monitors audio signals, identifies feedback conditions through frequency subband analysis, and automatically applies gain reduction to suppress howling, thereby eliminating the need for manual muting and maintaining user convenience.
Solution Approach 2:
The patent replaces the manual mechanical action of muting with an automated electronic signal processing system. By using digital signal processing to detect and suppress feedback automatically, the system substitutes the manual operation with an electronic control mechanism, thereby improving ease of operation while maintaining effective howling suppression.
3Measurement precision
If frequency subband analysis is performed to detect feedback, then detection precision improves, but computational complexity increases
Solution Approach 1:
The patent divides the audio frequency spectrum into multiple subbands and performs feedback detection independently in each subband. This segmentation approach improves detection precision by focusing on specific frequency ranges where feedback is likely to occur, while the modular structure of processing separate subbands independently helps manage computational complexity through parallel processing.
Solution Approach 2:
The patent applies feedback detection and suppression only to frequency subbands where feedback is detected, rather than processing the entire audio spectrum uniformly. By applying partial action only where needed, the system achieves high detection precision in critical areas while reducing overall computational complexity by avoiding unnecessary processing in unaffected frequency ranges.
Data Source
AI summary
A system configured to perform adaptive feedback reduction, such as howling suppression, to prevent feedback from occurring when two devices are acoustically coupled during a communication session. To reduce feedback between the acoustically coupled devices, a device monitors input audio data from a microphone and determines whether feedback is present in individual frequency subbands. For example, the device determines an expected value for a first subband using neighboring subbands (e.g., averaging subbands surrounding the first subband) and compares the expected value to an actual value for the first subband. If the actual value is noticeably higher than the expected value, the device determines that feedback is present in the first subband and attenuates the first subband. If the feedback is not present, the device passes the first subband without attenuation.